The presently described technology relates generally to alkyl lactyllactate compounds such as lauryl lactyllactate, and compositions comprising or incorporating such compounds. The presently described technology also relates generally to improved processes of making the alkyl lactyllactate compounds and derivatives thereof as well as compositions comprising or incorporating the same.
In the area of personal care, there is a desire for surfactants to be mild, salt-free and 100% active. Other desirable attributes include being in liquid form at room temperature, having a non-nitrogen containing structure, an ability to formulate in cold-mix applications, and an ability to perform as good as or better than existing surfactants.
For household, industrial and institutional cleaning products, both surfactants and solvents are important ingredients in these products. Desirable attributes for such products include the ability to emulsify, suspend or penetrate greasy or oily soils and suspend or disperse particulates, in order to clean surfaces; and then prevent the soils, grease, or particulates from re-depositing on the newly cleaned surfaces. For example, a laundry detergent product should desirably remove dirt from clothes and then keep the dirt in solution so that it is removed with the wash water instead of re-depositing on the washed clothes.
It is also desirable to have the ability to control the foaming of different household, industrial and institutional products depending on the desired end-use applications. For example, a liquid manual dish washing detergent preferably has the ability to foam in the presence of soil that is being removed from dishware. Yet, for a laundry detergent or dish washing detergent for use in a high efficiency washing machine, low foam is desired to achieve the best cleaning and to avoid excess foaming. Other desirable properties of such consumer products include the ability to clarify the formulation and to improve stability. For hard surface cleaners, it is desirable to have the ability to wet various surface types and couple or suspend soils to leave the surface free from residue in the form of streaking and/or filming.
It has been unexpectedly discovered that the alkyl lactyllactates of the present technology can meet one or more of the above desired attributes, among others. The alkyl lactyllactates can be incorporated into, for example, various compositions and used as surfactants, emulsifiers, skin feel agents, film formers, rheological modifiers, solvents, release agents, lubrication agents, conditioners, and dispersants, etc. Such compositions can be used in end-use applications including, but not limited to, personal care, as well as household and industrial and institutional cleaning products. They can also be used in oil field applications, gypsum foamers, paints and coatings, adhesives, or other applications requiring cold tolerance performance or winterization (e.g., applications requiring cold weather performance without the inclusion of additional volatile components).
U.S. Pat. Nos. 2,350,388 and 2,371,281 (Claborn) (the “Claborn patents”) generally describe that an alkyl lactyllactate can allegedly be produced by heating a mixture of a dry lactide and an anhydrous alcohol at a temperature of from 70° to 90° C. for a period of about 6 to 8 hours in the presence of an acid catalyst and under anhydrous conditions. The Claborn patents also generally describe alkyl lactyllactates asserted to have properties desirable for solvents and plasticizers, and for production of other plasticizers.
However, the process to prepare alkyl lactyllactates as described in the Claborn patents requires a solvent to be used in the reaction mixture, which is either an excess amount of the alcohol or an inert organic liquid, such as benzene. The Claborn patents also require a reaction temperature of above 70° C. It is desirable, however, to eliminate the use of solvents in the reaction process for producing alkyl lactyllactates and/or to have a process that can run at a lower reaction temperature. Further, the Claborn patents do not appreciate the control and effect of chirality on the properties of the resultant alkyl lactyllactate. Nor do the Claborn patents teach how to make alkyl lactyllactates with different chiralities. Additionally, the Claborn patents do not appreciate the effects of the choice of alcohol (e.g., primary vs. secondary or tertiary; fatty alcohol vs. a lower alcohol) on the product yield, purity of the product, and properties of the product. Further, the Claborn patents do not appreciate and disclose alkyl lactyllactates that can be used as surfactants, emulsifiers, skin feel agents, film formers, thickeners, rheological modifiers, etc., for personal care and other application areas. Thus, it is desirable to have a process that can produce a better yield of a higher purity alkyl lactyllactate product without distillation or other purification. It is also desirable to make and use an alkyl lactyllactate with a selected chirality to achieve or improve certain desired end-product properties.
U.S. Pat. No. 3,144,341 (Thompson) (the “Thompson patent”) discloses stearyl lactyllactate and cetyl lactyllactate produced by reacting stearyl alcohol or cetyl alcohol with lactic acid (2-hydroxypropionic acid, CH3CHOHCOOH). The stearyl lactyllactate and cetyl lactyllactate so produced are generally described as emulsifying agents particularly suitable as shortening agents in cake mixes and the like. The Thompson patent states that the reaction product is a mixture of stearyl lactyllactate and stearyl lactate, which are referred to as stearyl lactoyl lactate and stearyl lactate, respectively. Col. 3, lines 29-31. The Thompson patent further asserts that stearyl lactate is less effective than the desired stearyl lactyllactate. Col. 3, lines 56-57. The reference recommends using 2.1 moles of lactic acid per one mole of stearyl alcohol (or cetyl alcohol), col. 1, lines 31-54, but suggests that the reaction of stearyl lactyllactate with an additional mole of lactic acid offered no appreciable advantages. Col. 3, lines 57-59. The Thompson patent also does not teach or suggest the use of a catalyst for the reaction of the alcohol with lactic acid. Because it is believed that alkyl lactyllactates are more efficient, and can provide better performance and stability than alkyl lactates, it is desirable to have an improved process that can produce an alkyl lactyllactate product via a lactic acid route that contains a higher ratio of the lactyllactate component over the lactate component.